Diluted Earnings Per Share for Class A Common Shares Using If-Converted Method (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended				9 Months Ended
	Jan. 31, 2015		Jan. 31, 2014		Jan. 31, 2015		Jan. 31, 2014
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Undistributed & Distributed Earnings, Per Basic	$ 2,841		$ 2,477		$ 5,550		$ 7,763
Basic weighted average common shares outstanding	28,239		27,686		28,247		27,499
Diluted, Class A Common Shares	28,554		28,187		28,580		27,972
Basic, EPS	$ 0.10	[1]	$ 0.09	[1]	$ 0.20	[1]	$ 0.28	[1]
Diluted, EPS	$ 0.10	[1]	$ 0.09	[1]	$ 0.19	[1]	$ 0.28	[1]
Class A Common Shares
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Undistributed & Distributed Earnings, Per Basic	2,580		2,247		5,042		7,036
Undistributed & Distributed Earnings, Class B Conversion	261		230		508		727
Net Income (Loss) Available to Common Stockholders, Diluted, Total	$ 2,841		$ 2,477		$ 5,550		$ 7,763
Basic weighted average common shares outstanding	25,652		25,099		25,660		24,912
Common Stock Equivalents	315		501		333		473
Weighted Average Number of Shares Including Common Stock Equivalents, Diluted	25,967		25,600		25,993		25,385
Class B Conversion	2,587		2,587		2,587		2,587
Diluted, Class A Common Shares	28,554		28,187		28,580		27,972
Basic, EPS	$ 0.10		$ 0.09		$ 0.20		$ 0.28
Diluted, EPS	$ 0.10		$ 0.09		$ 0.19		$ 0.28

[1] Basic per share amounts are the same for Class A and Class B shares. Diluted per share amounts for Class A shares are shown above. Diluted earnings per share for Class B shares under the two-class method are $0.10 and $0.09 for the three months ended January 31, 2015 and 2014 and $0.20 and $0.28 for the nine months ended January 31, 2015 and 2014, respectively. See Note D to the Condensed Consolidated Financial Statements.